Thus, in a note dated December 1, 1963, the head of the FBI, Edgar Hoover, citing "a reliable source who was in Russia on the day of the murder," writes that the news of the Kennedy assassination in the USSR caused shock. The CPSU members feared that the murder could have been part of a conspiracy to bring the ultra-right circles to power in the United States.

As a result, it turned out what probably didn't happen this day this year:

One of Waldron's theories goes like this. President Kennedy and his brother, Attorney General Robert Kennedy, bitter about the disastrous 1961 Bay of Pigs invasion, in 1963 concocted a secret plan to stage a palace coup to unseat Fidel Castro with the aid of the US Army. The coup leader would declare martial law and proclaim a provisional government, then cut ties with the Soviet Union and join the United States in partnership. Robert Kennedy was personally in charge of this invasion plan. D-Day--or, rather, C-Day for coup day--was to be December 1st, 1963. But two weeks before that, President Kennedy was killed, and that was the end of the invasion plan.

Does anybody know anything meaningful else that happened or didn't happen that day?

So perhaps he just likes the golden apple of Kallisti with the date stamp "US1DEC1963".

While working as letters editor of Playboy, conspiracy researcher Robert Anton Wilson was inundated by Birch propaganda and decided to counter it by writing a satirical story about the Illuminati as if the society was an honest attempt to overthrow royalty and religion (and not some covert Jesuit plot to infect Freemasonry from within). Thornley immediately began corresponding with Wilson and worked his way into the pages of Playboy and eventually Discordianism became the foundation for Wilson’s trilogy, which began with a counterculture reporter’s investigation into the JFK assassination.